Lack of relationship between the direction of operant turning and horseradish peroxidase uptake by crossed nigro-striatal projections.

We examined the effect of training rats to perform an operant turning response on the crossed nigro-striatal projections. Rats were reinforced for circling behavior with water. After 7 days of reinforced circling, the animals were implanted with horseradish peroxidase in the striatum either ipsilateral or contralateral to the direction in which they had been trained to turn. Subsequently, the substantia nigra, ventral tegmental area, and retrorubral area in both hemispheres were examined for labeled cells. This analysis failed to reveal any relationship between the direction of reinforced circling and efferents from these areas to the striatum.